Reactive power quick response method of network construction type energy storage converter

Abstract

The invention discloses a reactive power quick response method of a network construction type energy storage converter, which is characterized in that a high-pass filter is connected in parallel on a virtual impedance voltage drop feedforward path, so that the transient support capability is skillfully improved while the steady-state current limiting is not influenced. And a steady-state component in the feed-forward signal is effectively filtered through the high-pass filter, so that the current limiting effect of the virtual impedance in a steady state is not weakened. Meanwhile, for the rapid current change in the transient process, the high-pass filter can enable the current to smoothly pass through, so that the output voltage is rapidly supported, the problem of steady-state current limiting failure caused by direct feed-forward is avoided, and the defect of slow reactive transient response is overcome. The method has higher flexibility, robustness and adaptability, can more stably and reliably improve the voltage source characteristics of the grid-forming type energy storage converter, and provides more effective voltage support for a power grid.

Description

Technical Field

[0001] This invention belongs to the field of new energy grid connection technology, specifically a reactive power fast response method for grid-type energy storage converters. Background Technology

[0002] Under the "high-voltage and high-efficiency" environment, the reliability risks of new power systems are increasing, with short-circuit faults being the most frequent and posing the greatest threat to the system. When responding to short-circuit faults, generation units avoid damage by disconnecting from the grid, thus failing to provide voltage support to the power system and potentially exacerbating grid faults, triggering a series of chain reactions. To improve the reliability of power systems in responding to short-circuit faults, domestic and international industry standards require energy storage converters to have low-voltage ride-through capabilities, ensuring they remain connected to the grid during faults while providing voltage support to the power system.

[0003] Energy storage converters serve as a bridge connecting energy storage units and the power grid, and can be broadly categorized into two types: grid-connected energy storage converters and grid-connected energy storage converters. Grid-connected converters can be equivalently represented as a current source connected in parallel with an equivalent impedance, relying on a phase-locked loop (PLL) to track the grid frequency and phase. When dealing with low-voltage faults, they employ a passive support method, requiring the output of corresponding reactive current based on current commands. Grid-connected energy storage converters, on the other hand, are power electronic devices capable of autonomously establishing and maintaining grid voltage and frequency. By simulating the external characteristics of a synchronous motor, they autonomously construct the grid connection point voltage, without relying on a PLL to obtain phase information, and externally present themselves as a voltage source connected in series with an equivalent impedance. When dealing with low-voltage ride-throughs, they actively generate reactive current to support the grid connection point voltage by utilizing their voltage source characteristics. Therefore, it can be seen that during low-voltage ride-throughs, grid-connected converters have a natural advantage in providing reactive power support to the power system, with a more pronounced effect and faster response.

[0004] Currently, the State Grid Testing Center's requirements for low-voltage ride-through testing of grid-type energy storage converters can be mainly divided into two aspects: Firstly, during the low-voltage ride-through period, when no current limiting occurs, the grid-type energy storage converter should compensate for reactive power according to the set reactive power regulation coefficient; when output current limiting occurs, it should output reactive power to the maximum extent within the current limit value. Secondly, the time from voltage drop to reactive current establishment should not exceed 30 ms (see reference: National Energy Solar Power Generation R&D (Experimental) Center. Original Records of Grid-type Energy Storage Converter Testing [Z]. Nanjing: 1st Edition, 1st Revision, 2024). In summary, this requires the grid-type energy storage converter to provide as much reactive current as possible in the shortest possible time to effectively support the grid voltage.

[0005] While grid-connected converters can respond to voltage dips in a relatively short time, traditional reactive power control strategies for grid-connected energy storage converters cannot establish a sufficient level of reactive current in a short period when dealing with low-voltage ride-throughs, resulting in insufficient reactive current response. Existing literature largely studies the current-limiting problem of grid-connected converters and how to generate reactive power as much as possible to support the grid during fault steady-state conditions, but it neglects the timeliness of grid-connected converters in supporting the grid. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention proposes a fast reactive power response method for grid-type energy storage converters. This method cleverly improves transient support capability without affecting steady-state current limiting by connecting a high-pass filter in parallel on the virtual impedance voltage drop feedforward path.

[0007] The technical solution of this invention to solve the aforementioned technical problem is: designing a reactive power fast response method for a grid-type energy storage converter. The grid-type energy storage converter in this method is an LCL-type three-phase NPC three-level voltage source inverter. The control method of this converter is a power outer loop and an inner loop control. The power outer loop adopts a virtual synchronous machine control method. The inner loop control is an improved design. Based on the voltage-current dual closed-loop control, a virtual impedance and a high-pass filter are added to provide inertia for the grid and support the grid connection point voltage. The specific process of the inner loop control is as follows: In the inner loop control circuit of the grid-type energy storage converter, a virtual impedance is connected in series and a high-pass filter is connected in parallel; the inner loop control includes two parts: a voltage outer loop and a current inner loop. The specific process is as follows: First, the internal potential amplitude of the reactive power loop output by the virtual synchronous machine control is... Subtracting the voltage drop across the virtual impedance yields the reference voltage for the outer voltage loop. The difference between this reference voltage and the actual output voltage is processed by the outer voltage loop PI regulator to generate the reference current for the inner current loop. Subsequently, the inverter-side inductor current value is acquired in real-time and subtracted from the reference current. This difference is then adjusted by the inner current loop PI regulator to output the current loop control signal. Simultaneously, the voltage drop across the virtual impedance is filtered through a high-pass filter to output a high-frequency dynamic component, i.e., the feedforward compensation signal. The current loop control signal and the feedforward compensation signal are then superimposed. The resulting signal is modulated to generate the converter's switching control signal. The converter is then regulated according to this switching control signal, thereby achieving rapid reactive power response.

[0008] Compared with existing technologies, the advantages of this invention are as follows: By connecting a high-pass filter in parallel on the virtual impedance voltage drop feedforward path, this invention cleverly improves transient support capability without affecting steady-state current limiting. The high-pass filter effectively filters out steady-state components in the feedforward signal, ensuring that the current-limiting effect of the virtual impedance in steady state is not weakened. Simultaneously, the high-pass filter allows rapid current changes during transient processes to pass smoothly, thereby achieving rapid support for the output voltage. This avoids the steady-state current limiting failure problem caused by direct feedforward and overcomes the drawback of slow reactive power transient response. Therefore, this invention has higher flexibility, robustness, and adaptability, and can more stably and reliably improve the voltage source characteristics of grid-connected energy storage converters, providing more effective voltage support for the power grid. Attached Figure Description

[0009] Figure 1 This invention provides a method for rapid reactive power response in a grid-type energy storage converter, using the main circuit topology of a three-phase NPC three-level voltage source inverter in one embodiment.

[0010] Figure 2 This is a block diagram of the active power control of a grid-type energy storage converter based on a virtual synchronous generator control strategy.

[0011] Figure 3 This is a block diagram of reactive power control for existing grid-type energy storage converters based on a virtual synchronous generator control strategy.

[0012] Figure 4 This is a block diagram of the inner loop control of a grid-type energy storage converter in the existing technology.

[0013] Figure 5 This invention provides a method for rapid reactive power response in a grid-type energy storage converter, and an equivalent voltage source circuit diagram of such a grid-type energy storage converter.

[0014] Figure 6 This is a power frequency small-signal model diagram corresponding to the virtual synchronous generator strategy of the existing grid-type energy storage converter.

[0015] Figure 7 This is a schematic diagram illustrating the setting of virtual impedance and high-pass filter in the inner loop control of an implementation of the reactive power fast response method for a grid-type energy storage converter according to the present invention.

[0016] Figure 8 The Simulink simulation main circuit diagram is shown for simulation testing of the reactive power fast response method of the grid-type energy storage converter of the present invention.

[0017] Figure 9 To utilize Figure 8The Simulink simulation main circuit uses an existing method (removing the high-pass filter in the method of this invention) to display the curves of active power, reactive power, phase voltage, and phase current during the reactive power response process in response to low voltage ride-through.

[0018] Figure 10 To utilize Figure 8 The Simulink simulation of the main circuit uses an existing method (removing the high-pass filter in the method of this invention) to determine the reactive power response time during low voltage ride-through.

[0019] Figure 11 To utilize Figure 8 The Simulink simulation main circuit uses the method of this invention to display the curves of active power, reactive power, phase voltage, and phase current during the reactive power response process in response to low voltage ride-through.

[0020] Figure 12 To utilize Figure 8 The Simulink simulation of the main circuit uses the method of this invention to achieve reactive power response time during low voltage ride-through. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below with reference to specific embodiments.

[0022] The main circuit topology used in this invention is as follows: Figure 1 As shown, this is a three-phase NPC three-level voltage source inverter: the DC side is supplied by a voltage source. With capacitor , The voltage divider system is used to invert the phases of the AC signal into three phases via a three-level NPC inverter (each phase containing switches and clamping diodes). After harmonics are filtered out by an LCL filter, the output is sent to the PCC grid connection point and then connected to the AC bus. The control structure can be mainly divided into an outer power loop and an inner loop control. The inductor on the LCL filter side closest to the inverter is called the inverter-side inductor, and the inductor on the other side is called the grid-side inductor.

[0023] The power outer loop of this invention adopts a virtual synchronous machine control method, and the specific control structure is as follows: Figures 2-3 As shown, by simulating the rotor motion equations and excitation characteristics of a synchronous generator, the converter acquires inertial response and damping characteristics similar to a synchronous generator, thereby enabling it to actively participate in grid frequency and voltage regulation and enhancing system stability. The inner loop control employs a voltage-current dual closed-loop configuration, controlling the output voltage and current separately. The specific control structure is as follows: Figure 4As shown. Meanwhile, to prevent the converter output current from exceeding the limit during fault ride-through, a virtual impedance current limit is introduced to limit the output current and ensure stable and reliable converter operation.

[0024] Based on the aforementioned control loop, this invention addresses the problems of weak voltage source characteristics and lag in reactive power response during fault transients in traditional voltage-current dual-loop control strategies that introduce virtual impedance limiting. It proposes adding an additional feedforward channel to the existing voltage-current dual-loop control, feeding the voltage across the virtual impedance forward to the PWM modulation stage after passing through a high-pass filter. This is equivalent to adding a transient controlled voltage source to the original power equivalent circuit, such as... Figure 5 As shown, this improves upon the reactive power response delay problem of traditional voltage-current dual closed-loop control, thereby significantly enhancing the voltage source characteristics of the grid converter under large disturbances and accelerating the reactive power response speed.

[0025] This invention provides a fast reactive power response method for a grid-connected energy storage converter. The grid-connected energy storage converter in this method is an LCL-type three-phase NPC three-level voltage source inverter. The control method of the converter is a power outer loop and an inner loop control. The power outer loop adopts a virtual synchronous machine control method. The inner loop control is an improved design. On the basis of voltage-current dual closed-loop control, a virtual impedance and a high-pass filter are added to provide inertia to the grid and support the grid connection point voltage.

[0026] The control block diagram of the virtual synchronous machine control method for the power outer loop of the converter is as follows: Figure 2-3 As shown, the control circuit is divided into two branches: active and reactive. The active side uses power frequency regulation simulating a synchronous machine, introducing inertia and damping elements. The reactive side uses the deviation between the reference voltage and the actual voltage as a droop element. After adjustment, it combines the reactive reference and actual reactive power effects, and then outputs an electromotive force through an integrator to simulate the reactive voltage regulation characteristics of a synchronous machine. The virtual synchronous machine control method of the converter's power outer loop is existing technology.

[0027] Depend on Figure 2-3 It can be seen that the active power loop simulates the inertia and primary frequency regulation of a synchronous generator, while the reactive power loop simulates the primary voltage regulation characteristics of a synchronous generator. The mathematical equations for the active power loop and the reactive power loop are as follows: (1) (2) In the formula: and These are the given reference values ​​for active and reactive power. The active-frequency droop factor; The reactive power-voltage droop factor; Angular frequency of the virtual synchronizer; This is the rated angular frequency of the virtual synchronizer; This represents the peak value of the converter output voltage. This is the effective value of the rated voltage of the converter; This is a virtual moment of inertia; The reactive power integral coefficient is used; it can be seen that the output of the active power loop of the virtual synchronous machine serves as the frequency and phase of the inverter modulation wave, while the output of the reactive power loop serves as the amplitude of the inverter modulation wave. The active power fed into the grid by the converter... and reactive power The expression is: (3) (4) (5) In the formula: Indicates the converter output voltage With grid voltage The phase difference between them; This represents the line inductive reactance. First, the small-signal model of the virtual synchronous machine is derived. The state equations in the time domain are then subjected to small perturbations and linearized under the rated operating voltage. Finally, a Laplace transform is performed on the linearized time-domain equations.

[0028] (6) In the formula: , , , , These are the angular frequency, power angle, amplitude of internal potential, active power, and reactive power of the output voltage during steady-state operation of the virtual synchronous machine. , , , , These are the small disturbances near the corresponding DC operating point, i.e., the disturbance components superimposed on the average value of each state variable over one switching cycle when the system is in periodic steady state. Substituting equation (6) into equations (1)-(5), and considering the following approximate relationship: , , , , By eliminating the direct current and neglecting disturbances of degree two or higher on both sides of the equation, we obtain: (7) (8) (9) (10) (11) Taking the Laplace transform of the linearized time-domain equations, we get: (12) (13) (14) (15) (16) According to equations (12)-(16), the power frequency small-signal model of the virtual synchronizer in the s (complex frequency domain) can be obtained, such as Figure 6 As shown. When the grid strength is high (characterized by high power, strong current, and low frequency), the power angle of the virtual synchronous machine... It is usually less than 0.1 pu. As can be seen from the formula, when When the coefficients are small, the coupling terms are very small and can be ignored. Therefore, when designing power switching circuits, the active and reactive loop parameters can be designed independently.

[0029] Therefore, the open-loop transfer functions of the active and reactive power loops (i.e., the ratio of the Laplace transform of the output signal to the Laplace transform of the input signal, where s is a complex frequency domain variable) are shown in equations (17) and (18). It can be seen that the open-loop transfer function of the active power loop is a second-order element, while the open-loop transfer function of the reactive power loop is a first-order element because it lacks an integral element. This provides a basis for subsequent parameter design.

[0030] (17) (18) The specific process of the inner loop control is as follows: In the inner loop control circuit of the grid-type energy storage converter, a virtual impedance is connected in series and a high-pass filter is connected in parallel. This inner loop control consists of two parts: a voltage outer loop and a current inner loop. The specific process is as follows: First, the internal potential amplitude output by the reactive power loop controlled by the virtual synchronous machine is... Subtracting the voltage drop across the virtual impedance (the voltage difference between the input and output terminals of the virtual impedance) yields the reference voltage for the outer voltage loop. This reference voltage is then subtracted from the actual output voltage, and the result is processed by the outer voltage loop PI regulator to generate the reference current for the inner current loop. Subsequently, the inverter-side inductor current value is acquired in real-time, subtracted from the reference current, and the result is further adjusted by the inner current loop PI regulator to output the current loop control signal. .like Figure 7As shown, the voltage drop across the virtual impedance is simultaneously filtered by a high-pass filter to output the high-frequency dynamic component, i.e., the feedforward compensation signal. u v Then, the current loop control signal and the feedforward compensation signal are superimposed, as shown in equation (19) below. The resulting signal is... u * pwm After modulation, the switching control signal of the converter is generated. The converter is then regulated according to the switching control signal to achieve rapid response of reactive power.

[0031] (19) The feedforward compensation signal is applied to the actual output voltage of the grid-type energy storage converter to further enhance the dynamic response performance of the system. Through this structure, a high-pass filter is used to extract the dynamic component from the virtual impedance voltage drop and inject it into the modulation path, effectively improving the system's damping characteristics and dynamic response speed, thereby achieving rapid reactive power response.

[0032] The design of the virtual impedance is mainly to ensure that the converter output current does not overcurrent when a voltage drop occurs. The design of the virtual impedance parameters is guided by equations (20) and (21), taking into account the magnitude of the current limit value and the grid inductive reactance.

[0033] (20) (twenty one) In the formula: This represents the peak value of the converter output voltage. Indicates the current limiting value of the converter; Indicates virtual resistance; Indicates virtual inductance; This represents the grid-side inductive reactance, which is the product of the inductance value of the grid-side inductance and the angular frequency of the grid voltage. This represents the impedance ratio of the virtual impedance. It's worth noting that the virtual impedance should be inductive overall to ensure proper reactive current response. According to the settings Substitute the values ​​of into formulas (20) and (21) to obtain the values ​​of virtual resistance and virtual inductance. Then, amplify the above values ​​of virtual resistance and virtual inductance by 20% to obtain . , The optimal range of values.

[0034] This calculation method can provide a reference for determining the virtual impedance value, allowing for fine-tuning within the suggested impedance ratio range while meeting the minimum theoretical value and considering actual conditions. and Generally, increasing It can enhance damping, but may affect steady-state accuracy, and will slow down dynamic response; increasing It can enhance inductive support, but it can only output maximum reactive power support when the equivalent output impedance of the converter matches the grid impedance.

[0035] The voltage drop across the virtual impedance is calculated as follows: First, the three-phase current signal of the inverter-side inductor, which is acquired in real time, is transformed into a synchronous rotating coordinate system, as shown in equation (22). The coordinate transformation matrix is ​​represented using a constant magnitude transformation. This indicates the angular velocity of synchronous rotation.

[0036] (twenty two) (twenty three) Using the virtual impedance parameter, calculate the voltage drop component on the virtual impedance of the dq axis, as shown in formula (24).

[0037] (twenty four) The angular frequency of the grid voltage; .

[0038] In order not to affect the current limiting effect of the virtual impedance under the steady state of the fault, a high-pass filter is connected in parallel on the voltage drop across the virtual impedance to block low-frequency signals, retaining only the feedforward effect during the fault transient period.

[0039] The voltage drop across the virtual impedance is input to the high-pass filter to obtain a high-frequency feedforward compensation signal. Finally, the output signal of the high-pass filter is added to the current loop control signal and then input to the modulation stage. The transfer function of the high-pass filter is shown in equation (25), where... This represents the cutoff angular frequency of the high-pass filter.

[0040]

[0041] The specific design of the cutoff frequency of the high-pass filter can be rewritten from equation (25) to equation (26): (26) in This indicates the cutoff frequency of the high-pass filter. This indicates the frequency of the input signal. Based on the signal rise time... With bandwidth The engineering approximation relationship is given by equation (27): (27) For a low-pass filter, there is . This refers to the reactive power response time. Based on the set reactive power response time, the cutoff frequency of the high-pass filter can be obtained. The maximum value is then reduced by a factor of 1.5 to obtain the optimal range of values ​​for the cutoff frequency of the high-pass filter.

[0042] exist , Within the optimal range of values ​​for both the high-pass filter and the cutoff frequency, different values ​​were calculated using digital simulation methods. , , The active power output and reactive power response time of the grid-type energy storage converter under different grid voltage dip conditions (i.e., all settings are the same except for the amount of grid voltage dip, specifically ranging from 3% to 90%) are set. The reactive power response time is not greater than the set value and has the smallest average value. , , The optimal value combination is the combination of values ​​chosen. When no combination with the smallest mean exists, combinations where the reactive power response time under each grid voltage drop condition is selected, and the normalized mean of the reactive power response time for each combination is calculated. The combination with the smallest mean is the optimal value. The desired value is then determined. , , When the optimal value is substituted into the inner loop control of the above-mentioned grid-type energy storage converter, a rapid reactive power response can be achieved when the grid voltage drops.

[0043] The aforementioned digital simulation methods can be implemented on simulation platforms such as MATLAB / Simulink and PSCAD / EMTDC.

[0044] Example The technical effects of the method of the present invention are verified below with reference to specific embodiments. The specific parameters of the grid-type energy storage converter are shown in Table 1.

[0045] Table 1 Three-phase VSG parameters

[0046] This embodiment proposes a method to accelerate the reactive power response of a grid-type energy storage converter. The specific design steps of this method are as follows: Assuming a 1 Hz change in grid voltage frequency results in a 100% change in inverter output active power (60 kW); and a 50% change in grid voltage amplitude results in a 100% change in inverter output reactive power (60 kVA), then:

[0047]

[0048] At the active loop cutoff frequency At this point, the magnitude of the system loop gain is equal to 1, then according to equation (17), we can obtain:

[0049] Solving equation (30) yields: (31) Take here It is 5 Hz, from which we can conclude .

[0050] Similarly, the reactive power loop at the cutoff frequency At this point, the magnitude of the system loop gain is equal to 1, and according to equation (18): (32) Solving equation (32) yields: (33) With the same cutoff frequency, the reactive power loop only has a first-order low-pass filter and lacks an integrator. To improve the reactive power loop's ability to suppress grid voltage ripples, its loop bandwidth is generally lower than that of the active power loop; here, we take... Then, according to equation (32), we can obtain .

[0051] The voltage-current inner loop design can refer to the following formula (this is existing technology; for details, please refer to: Yazdani A, Iravani R. Voltage-Sourced Converters in Power Systems: Modeling, Control, and Applications[M]. Hoboken, NJ: Wiley, 2010.): (34) In the formula, , , , These represent the PI parameters of the current loop. , These represent the PI parameters of the voltage loop. The parasitic resistance of the inverter-side inductor is 0. According to equation (34), we can calculate: (35) In a strong grid environment, assuming the grid voltage is at this time... Fall to At this point, the voltage drop between the inverter output voltage and the dropout point is almost entirely borne by the virtual impedance.

[0052] Pick , , Let be the rated operating current of the converter. Then, the specific value of the virtual impedance is calculated using equations (20) and (21). Simultaneously, to ensure the current does not exceed the limit, the calculated virtual resistance is increased by approximately 20%. Finally, the calculated... Based on the calculated virtual impedance values, the voltage drop components on the virtual impedance of the dq axis are calculated respectively, as shown in formula (36), and used as the initial feedforward compensation signal.

[0053] (36) The feedforward signal also needs to be superimposed with a high-pass filter to block low-frequency signals, thereby preserving the feedforward effect during the fault transient. Assuming the required reactive power response time is within 30 ms, for the low-pass filter, we can obtain from formula (27): (37) This means that in order not to affect the response speed of reactive power, the cutoff frequency selected for the high-pass filter is... smaller than It is important to note that excessively high cutoff frequencies can lead to attenuation of high-frequency signals, diminishing the feedforward effect. Conversely, lower cutoff frequencies may not adequately attenuate low-frequency signals, increasing the attenuation effect of the feedforward signal on the virtual impedance current limiting and potentially causing overcurrent. Ultimately, through numerical simulation optimization combined with experimental data, a cutoff frequency was selected that optimizes the system's dynamic performance without compromising steady-state quality, while ensuring response speed. Through practical verification and computational estimation, the cutoff frequency of the high-pass filter was finally selected. .

[0054] The effectiveness of this feedforward measure was verified through a low-voltage ride-through test using simulation methods. If, at the moment of voltage drop, the reactive power response time using this invention is shorter than the reactive power response time without this measure, it indicates that this invention can reduce the reactive power response time of the grid converter to a certain extent and enhance the resilience of the equivalent voltage source, meaning that the method of this invention is effective.

[0055] At t=0.5 s, the grid voltage suddenly dropped from 1.0 pu to 0.3 pu. The effectiveness of the invention was verified by the reactive power response time. First, a low-voltage ride-through test was performed without the strategy proposed in this invention, and the results are as follows... Figure 9 , 10As shown, the response time is 33 ms. Then, the virtual impedance voltage feedforward (i.e., the output of the high-pass filter) is connected to the current loop output, and the low-voltage ride-through test is performed again. The results are as follows. Figure 11 , 12 As shown, after adopting the measures proposed in this invention, the response time was reduced from 33 ms to 25 ms, a reduction of approximately 24%, verifying the effectiveness of the method. Furthermore, a comparison of the results shows that the high-pass filter used in this invention has no effect on low-voltage ride-through steady-state conditions. Only during voltage dips, due to the enhanced short-time voltage source characteristics of the grid-type energy storage converter, the power grid can also be considered an equivalent voltage source. The parallel connection of two voltage sources causes voltage waveform oscillations. This phenomenon can be improved by adjusting the cutoff frequency of the high-pass filter, which will not be explained in detail here.

[0056] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

[0057] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A reactive power fast response method for a grid-type energy storage converter, wherein the grid-type energy storage converter in this method is an LCL-type three-phase NPC three-level voltage source inverter, and the control mode of the converter is power outer loop and inner loop control, wherein, The power outer loop adopts a virtual synchronous machine control method. Its feature is that the inner loop control is an improved design. On the basis of voltage-current dual closed-loop control, a virtual impedance and a high-pass filter are added to provide inertia for the power grid and support the voltage at the grid connection point. The specific process of the inner loop control is as follows: In the inner loop control circuit of the grid-type energy storage converter, a virtual impedance is connected in series and a high-pass filter is connected in parallel; the inner loop control includes two parts: a voltage outer loop and a current inner loop. The specific process is as follows: First, the internal potential amplitude of the reactive power loop output by the virtual synchronous machine control is... Subtracting the voltage drop across the virtual impedance yields the reference voltage for the outer voltage loop. The difference between this reference voltage and the actual output voltage is processed by the outer voltage loop PI regulator to generate the reference current for the inner current loop. Subsequently, the inverter-side inductor current value is acquired in real-time and subtracted from the reference current. This difference is then adjusted by the inner current loop PI regulator to output the current loop control signal. Simultaneously, the voltage drop across the virtual impedance is filtered through a high-pass filter to output a high-frequency dynamic component, i.e., the feedforward compensation signal. The current loop control signal and the feedforward compensation signal are then superimposed. The resulting signal is modulated to generate the converter's switching control signal. The converter is then regulated according to this switching control signal, thereby achieving rapid reactive power response.

2. The reactive power fast response method for a grid-type energy storage converter according to claim 1, characterized in that, The design of virtual impedance parameters is guided by equations (20) and (21); (20) (21) In the formula: This represents the peak value of the converter output voltage. Indicates the current limiting value of the converter; Indicates virtual resistance; Indicates virtual inductance; This represents the grid-side inductive reactance, which is the product of the inductance value of the grid-side inductance and the angular frequency of the grid voltage. The impedance ratio representing the virtual impedance. According to the settings Substitute the values ​​of into formulas (20) and (21) to obtain the values ​​of virtual resistance and virtual inductance. Then, amplify the above values ​​of virtual resistance and virtual inductance by 20% to obtain . , The optimal range of values.

3. The reactive power fast response method for a grid-type energy storage converter according to claim 1, characterized in that, The voltage drop across the virtual impedance is calculated as follows: First, the three-phase current signal of the inverter-side inductor, which is acquired in real time, is transformed into a synchronous rotating coordinate system, as shown in equation (22). The coordinate transformation matrix is ​​represented using a constant magnitude transformation. Indicates the angular velocity of synchronous rotation; (22) (23) Using the virtual impedance parameter, calculate the voltage drop component on the virtual impedance of the dq axis respectively, as shown in formula (24); (24) in, , Indicates virtual resistance; This represents a virtual inductance.

4. The reactive power fast response method for a grid-type energy storage converter according to claim 2, characterized in that, The transfer function of the high-pass filter is shown in equation (25), where This indicates the cutoff angular frequency of the high-pass filter; ， The specific design of the cutoff frequency of the high-pass filter can be rewritten from equation (25) to equation (26): (26) in This indicates the cutoff frequency of the high-pass filter. Indicates the frequency of the input signal; based on the signal rise time With bandwidth The engineering approximation relationship is given by equation (27): (27) For a low-pass filter, there is ; This refers to the reactive power response time. Based on the set reactive power response time, the cutoff frequency of the high-pass filter can be obtained. The maximum value is then reduced by a factor of 1.5 to obtain the optimal range of values ​​for the cutoff frequency of the high-pass filter.

5. The reactive power fast response method for a grid-type energy storage converter according to claim 4, characterized in that, In virtual resistance Virtual inductance Within the optimal value range and the cutoff frequency of the high-pass filter. Within the optimal value range, different values ​​are calculated using digital simulation methods. , , The active power output and reactive power response time of the grid-type energy storage converter under different grid voltage dip conditions are measured with different value combinations. The reactive power response time is not greater than the set value and has the smallest average value. , , The optimal value combination is the combination of values ​​chosen. When no combination of values ​​with the smallest mean exists, combinations where the reactive power response time under each grid voltage drop condition is not greater than a set value are selected. The normalized mean of the reactive power response time under each combination is calculated, and the combination with the smallest mean is the optimal value. The desired value is then... , , When the optimal value is substituted into the inner loop control of the above-mentioned grid-type energy storage converter, a rapid reactive power response can be achieved when the grid voltage drops.

6. The reactive power fast response method for a grid-type energy storage converter according to claim 5, characterized in that, The voltage drop range is specifically set from 3% to 90%.

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